Both natural and synthetic polymers, including homopolymers and copolymers, which are both biocompatible and biodegradable in vivo are known for use in the manufacture of medical devices that are implanted in body tissue and that are absorbed or passed by the body over time. Examples of such medical devices include suture anchor devices, sutures, staples, surgical tacks, clips, plates, screws, drug-delivery devices, adhesion prevention films and foams, and tissue adhesives.
Natural polymers may include catgut, cellulose derivatives and collagen. Natural polymers typically are absorbed by the body after enzymatic degradation of the polymers in the body.
Synthetic polymers may include aliphatic polyesters, polyanhydrides and poly(orthoester)s. Such polymers typically degrade by a hydrolytic mechanism in the body and then are absorbed by the body. Such synthetic polymers include homopolymers, such as poly(glycolide), poly(lactide), poly(e-caprolactone), poly(trimethylene carbonate) and poly(p-dioxanone), and copolymers, such as poly(lactide-co-glycolide), poly(e-caprolactone-co-glycolide), poly(glycolide-co-trimethylene carbonate), poly(alkylene diglycolate), and polyoxaesters. The polymers may be statistically random copolymers, segmented copolymers, block copolymers or graft copolymers.
Alkyd-type polyesters prepared by the polycondensation of a polyol, polyacid and fatty acid are used in the coating industry in a variety of products, including chemical resins, enamels, varnishes and paints. These polyesters also are used in the food industry to make texturized oils and emulsions for use as fat substitutes.
While much progress has been made in the field of polymeric biomaterials, further developments must be made in order for such biomaterials to be used optimally in the body. There is a great need for polymers for use in drug delivery, tissue engineering and medical devices, where the polymers have functional pendant groups that would allow, e.g., attachment of drugs, improvement of biocompatibility or promotion of bioadhesion. Polyesters containing functional comonomers are known. However, the chemistry involved in the synthesis of functional monomers is often very complex and results in poor yields.